Various fluids, such as water and water in solution with other substances, such as alcohol, have been commonly injected into hydrocarbon-fueled engines to provide improved engine operation. During the compression stroke, the water droplets vaporize and absorb heat energy produced within the combustion chamber to prevent pre-ignition. The vaporized water is subsequently heated by the burning fuel mixture during the power stroke and expands, increasing the mechanical efficiency of the combustion process. Beneficial side effects may include the prevention of carbon buildup on the cylinder walls of the engine. As a result of the beneficial effects of the water injection, the engine is able to run more smoothly and efficiently on a leaner fuel mixture. Additionally, the reduction in peak combustion chamber temperatures reduces the formation of oxides of nitrogen (Nox), and minimizes thermal stresses on engine components.
Various types of devices have been developed to introduce fluids into the intake air of internal combustion engines. These devices have included nozzle-type injectors in which the fluid is pumped directly into the engine, emulsion injection systems, and intake air humidifiers in which air is passed through a volume of water before being introduced into the engine. Direct injection of the fluid into the intake air has been limited by the inability of mechanical systems to precisely meter a relatively small volume of water to obtain an optimum volumetric ratio of water in the final fuel/air charge. Humidified air systems are impractical as the majority of the heat absorption capacity of the water lies in the phase transformation from liquid to gas.
Prior art systems have not been entirely successful to responses in engine requirements, largely due to the inability of purely mechanical devices to respond over a wide range in conditions. A method of supplying two different fluids to a common combustion chamber is described in U.S. Pat. No. 4,031,864 to W. T. Crothers. Water is used to achieve phase separation when methanol and gasoline are stored in a common tank, but are pumped from different levels within that tank. The primary purpose of this invention is to allow the use of two different fuels.
A method of supplying water during peak power demand periods in an internal combustion engine is described in U.S. Pat. No. 4,351,289 to V. A. Renda. Water injection is carried out with water from a reservoir pressurized by an injection pump which is energized only above predetermined torque demand levels, under the control of a vacuum switch sensing intake manifold vacuum.
A method of supplying water to an internal combustion engine for the purpose of allowing operation with leaner fuel mixtures is described by U.S. Pat. No. 4,461,245 to M. Vinokur. Intake manifold pressure is used to control the output of a water pump, thereby making the water injection rate responsive to engine load.
A method of providing water to the cylinders of turbocharged engines is described by U.S. Pat. No. 4,558,665 assigned to L. Sandberg. This system injects water into each cylinder individually and operates independently of the fuel system.
A system for water injection into internal combustion engines used to power generators is described by U.S. Pat. No. 4,960,080 to J. O'Neill, E. Schisler, and P. Kubo. The system is activated when the output current of the generator reaches a predetermined level which is associated with the onset of NO.sub.x emissions by the drive motor.
A system for injecting water into internal combustion engines having a spark ignition systems is described by U.S. Pat. No. 4,096,829 to G. Spears. The system operates a water injection pump at a rate proportional to engine RPM, where the RPM is sensed inductively off one of the ignition wires. Water injection rate is controlled by air flow through an atomizer.
A system for injecting water into a carburetor to allow operation with leanar fuel mixtures is described by U.S. Pat. No. 4,448,153 to R. Miller. A water injection pump is cycled on and off in response to such engine parameters as engine temperature, oil pressure and manifold pressure.
The prior art devices suffer from several problems. In general, they fail to provide a means of injecting water and fuel which is accurate enough to optimize fuel consumption over a wide range of operating conditions and power demand. Prior art systems also fail to provide a means of responding quickly to engine needs. The amount of water necessary to prevent preignition is relatively small, compared to the fuel injection rate. Prior art systems which relied on the starting and stopping of a water pump to control the water injection rate can not efficiently respond to dynamic engine operating conditions. Systems which rely solely on intake manifold pressure and engine RPM do not adequately control the water injection rate in a manner which is responsive to the need for cooling of the fuel charge during the compression stroke. The result is overly complex systems which do not address the root cause of preignition when operating an internal combustion with a lean fuel mixture, and, therefore, do not optimize engine performance.
It is an object of the present invention to provide a system for injecting fuel and a fluid, such as water into the intake air side of an internal combustion engine in response to engine operating parameters to optimize engine operation.
It is another object of this invention to provide a method of injecting fuel in response to engine load and at minimum concentrations necessary for efficient combustion.
It is another object of this invention to provide a method of injecting water in response to the rate of air intake and the rate of fuel injection.
It is another object of this invention to provide a method of injecting fuel and water in which optimum injection rates are achieved by controlling an electronic signal to electronic injectors in response to the rate of air flow through the intake manifold and the amount of power demanded by the operator.
It is another object of this invention to provide a fuel and water injection system which is inexpensive to manufacture and which is simple and reliable in operation.
It is another object of this invention to provide a means of reducing peak cylinder temperatures by absorbing some of the heat produced during the compression stroke in an internal combustion engine.
It is another object of this invention to minimize the production of oxides of nitrogen (NO.sub.x) by reducing peak cylinder temperatures during the combustion process.
It is another object of this invention to increase the mechanical efficiency of internal combustion engines by minimizing the pressure buildup during the compression stroke by absorbing some of the heat generated in the gasses during said compression stroke.
It is another object of this invention to increase the mechanical efficiency of an internal combustion engine by adding gaseous water vapor which will increase the expansion volume of cylinder gasses during the power stroke.
It is another object of this invention to provide a means of operating a higher compression engine on traditional fuels without premature ignition.